textproduct: Albany

WHAT HAS CHANGED

Flash Flood Watch issued for Ulster, Dutchess and Litchfield Counties for late tonight through Tuesday morning. The Slight Risk for Excessive Rainfall has been expanded across more of the area for Monday into Monday Night.

KEY MESSAGES

1) A widespread rainfall is expected late today through early Tuesday with the heaviest amounts likely across the mid-Hudson Valley into Litchfield County, CT. Isolated to scattered flash flooding will be possible, especially within urban and poor drainage areas.

DISCUSSION

KEY MESSAGE 1...

A stationary boundary will be stalled just south of the region over the northern mid Atlantic States and waves of low pressure will slowly move along this front between late today and Tuesday. With this stagnant pattern in places, periods of showers and embedded thunderstorms are expected to develop and slowly drift across our area from late today through early Tuesday morning. Some areas will see repeated rounds of showers and thunderstorms, which will allow for a threat for excessive rainfall and flash flooding.

PWAT values are expected to exceed 2 inches in the mid Hudson Valley, with lowering values further to the north. The values across southern areas are about 150%-180% of normal, which is about 2 STD above normal. Model soundings are showing plenty of signs for excessive rainfall, including a moist profile throughout the column, skinny CAPE profile, high PWATs and surface dewpoints and a high freezing level, indicating the potential for warm-rain processes and efficient rainfall production. Rainfall rates may easily exceed 1 inch per hour within showers and thunderstorms with this setup. The 00z SPC HREF PMM 3hr totals shows pockets of 1-2 inches of rainfall within the high terrain of our southern areas, which are impressive amounts for an ensemble. Even the NBM has up to 30% across southern areas for 6-hr rainfall totals exceeding an inch, which is also noteworthy for blended guidance.

CAMs suggest periods of repeated showers and thunderstorms will occur across far southern areas, although the exact northern extent does vary within the different guidance and it's unclear just how far north the steadier and heavier showers will get. There are also differences showing where the heaviest rainfall totals will be. While many models show bullseyes of several inches of rainfall, they vary whether these will be within or just south of our area. Still, there is enough confidence for the potential for heavy rainfall and possible flash flooding to go with a Flash Flood Watch for Ulster, Dutchess and Litchfield Counties. WPC has also increased their Day 2 (Mon into Mon Night) outlook to include a Slight Risk (Level 2 of 4) over much of southeastern NY and western New England. Isolated to scattered incidents of flash flooding is expected to occur, especially within urban and poor drainage areas. It won't be surprising for somewhere within the Northeast to see a localized rainfall total in excess of 5 inches with this system, but it's exact location is still very unknown at this time.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

Flying conditions are generally VFR to start the day with some broken mid and high level clouds. There was some MVFR mist overnight at KPOU, but this is starting to dissipate.

During the day today, flying conditions will be VFR through most of the day. BKN-OVC mid and high level clouds will continue with some lower clouds around 5-7 becoming thicker by the afternoon and evening hours. A few showers may spread towards KPOU towards sunset, with a better chance for a period of steadier rainfall there during tonight. Visibility may lower to MVFR within any showers near KPOU this evening into the first part of tonight. Some thunder can't be ruled out, but it doesn't appear widespread enough to include in the TAF just yet. Light winds from the east are expected for today.

Rainfall will become steadier and heavier at KPOU during the overnight hours, especially after 06z. Some IFR conditions, mainly for visibility, is expected at KPOU for the late night hours within moderate to possibly heavy showers. Meanwhile, the rainfall will be spreading northward, but it will be a slow process. Some showers may get close to KPSF and KALB towards daybreak. For now, will just address with a VCSH for KALB and a few hours of MVFR showers at KPSF towards the end of the TAF period. KGFL will be far enough north to avoid the rain through 12z Monday. Winds for all sites will be very light or calm from an east to southeast direction.

Outlook...

Monday Night: High Operational Impact. Likely SHRA. Tuesday: Moderate Operational Impact. Chance of SHRA. Tuesday Night: Low Operational Impact. Slight Chance of SHRA. Wednesday: No Operational Impact. NO SIG WX. Wednesday Night: No Operational Impact. NO SIG WX. Thursday: Moderate Operational Impact. Chance of SHRA...TSRA. Thursday Night: Moderate Operational Impact. Chance of SHRA...TSRA. Friday: High Operational Impact. Likely SHRA...TSRA.

ALY WATCHES/WARNINGS/ADVISORIES

CT...Flood Watch from late tonight through Tuesday morning for CTZ001-013. NY...Flood Watch from late tonight through Tuesday morning for NYZ063>066. MA...None. VT...None.